An adjustable-speed water driven turbine can comprise a rotor mounted on a shaft so as to be rotatable about a rotor axis and having a plurality of curved vanes, a variable nozzle in a water-entrance opening of the device and a control device for control of the flow of water through the turbine.
A free jet turbine for a traveling sprinkling irrigating device is taught in Austrian Pat. No. 352,460, in which the direction of the free jet is controllable in order to change the turbine speed. The water stream flowing through the turbine nozzle can be divided by a steel deflector so that it is not longer concentrated as it reaches the turbine vanes and a part of the energy contained in the stream is dissipated.
The deflector shifted in front of the nozzle acts to provide an uncontrollable turbulence and spraying and uniform control of the rotational speed can thus not be attained over a wide range.
By the uniformly high flow speed in the nozzle and the associated turbulence resulting from the stream deflector, an undesirably strong pressure drop occurs in the turbine because of the flow and friction losses. To change the direction of the free jet the nozzle is supported pivotally in a relatively costly construction.
A turbine for a spraying mechanism is described in the Austrian Pat. No. 364,566. The housing of the turbine has a substantially tangential feed pipe and a control device for the rotational speed of the turbine is provided which depends, in a reel driving irrigator, on the pipe draw-in or take up speed. This control device comprises a controlling valve or flap mounted in the vicinity of the mouth of the feed pipe by which the size of the cross section of the mouth of the feed pipe and the stream direction of the water fed into the turbine is changed.
Austrian Pat. No. 377,676 describes a water turbine, advantageously for a sprinkling device, in which in the vicinity of the entrance opening and advantageously also in the vicinity of the adjacent portion of the water feed tube a movable wall portion determining the flow cross section is provided. The movable wall is adjustable by a cam engaging it from the outside.
A change of the entrance flow momentum is possible because of this structure. The second of the two drive components, namely the pulling device above all can not be influenced.
Consequently an optimum adjustment of the entrance cross section and the annular clearance in the turbine to minimize shock losses is not possible.